Paolo Cavacini

Benthic algal mats of some lakes of Inexpressible Island (northern Victoria Land, Antarctica)

Benthic algal mats from four lakes located on Inexpressible Island (northern Victoria Land, Antarctica) were studied, analysing their structure and floristic composition. Thirty taxa of algae were identified: 11 Cyanophyta, 15 Bacillariophyta and 4 Chlorophyta. The lake mats contained from 15 (lake C) to 26 species (lake D). The number of diatom frustules in the mats varied from 771×103 (lake C) to 9428×103 frustules g-1 (lake B). In terms of floristic composition and macromorphology, these mats were observed to be very similar to moat mats described from Lake Gondwana (northern Victoria Land) and the Dry Valleys lakes of southern Victoria Land.

Floristic studies on freshwater algae of Lake Gondwana Northern Victoria Land (Antarctica)

Benthic algal mats and phytoplankton of Lake Gondwana (Northern Victoria Land, Antarctica) were investigated. Biomass, chlorophyll content and floristic analyses were carried out on algal mats. The mats are composed of two layers different in colour, floristic composition and chlorophyll content. The algal flora of the mats amount to 34 taxa (19 Cyanophyta, 7 Bacillariophyta, 8 Chlorophyta). The phytoplankton community is species-poor (only 5 taxa). Crytophyta account for about 98% of total algal density.

DIATOMS (BACILLARIOPHYTA) IN PHOTOTROPHIC BIOFILMS COLONISING AN ITALIAN WASTEWATER TREATMENT PLANT

The diatom assemblages within phototrophic biofilms in secondary treatment tanks of the Fiumicino Airport (Rome, Italy) wastewater treatment plant were investigated. Qualitative and quantitative comparisons were made between assemblages in sedimentation and chlorination tanks, on the tank walls and artificial substrata, on four sampling occasions. The assemblages were characterised by a rather stable species composition, low species diversity and dominance of raphid taxa. Correspondence analysis of diatom relative abundance data with regard to seasonal, site and substratum variation revealed both temporal and spatial differences in species assemblages. Rather than species composition changing over time between different sampling sites and surfaces, the proportional contributions of individual species to the assemblages varied with season. Biovolume data indicated that this outdoor system supported extensive diatom growth (high diatom biomass productivity). The potential use of autochthonous, diatom biofilms in tertiary wastewater treatment (removal of residual nutrients and pollutants) as opposed to conventional physico-chemical technologies is discussed with respect to the protection of receiving water bodies and the development of sustainable waste treatment.

NAVICULA SKUAE SP. NOV., A FRESHWATER DIATOM FROM CONTINENTAL ANTARCTICA

The freshwater diatom Navicula skuae sp. nov. is described from benthic and floating algal mats of some lakes in northern Victoria Land (Antarctica). The detailed morphology of this species is examined using scanning electron microscopy (SEM). Navicula skuae is compared with other similar species.

MORPHOLOGY, ECOLOGY AND DISTRIBUTION OF AN ENDEMIC ANTARCTIC LACUSTRINE DIATOM: CHAMAEPINNULARIA CYMATOPLEURA COMB. NOV.

Specimens belonging to the diatom species Pinnularia cymatopleura collected from benthic cyanobacterial mats of lakes and ponds in Continental Antarctica were examined. In addiction, slides from the West & West collection which contain isotypes of this taxon were also investigated. Light Microscope (LM) and Scanning Electron Microscope (SEM) studies of this diatom reveal that its valve structure possesses features typical of the recently established diatom genus Chamaepinnularia. The most important features that justify the allocation of this taxon to Chamaepinnularia are: — the presence of uniseriate striae composed of alveoli occluded by external hymenes; — the absence of multiseriate round poroids in the outer wall; — internally an apical series of apertures, located on the valve face separated from a second series on the valve mantle. The new combination Chamaepinnularia cymatopleura (West & G. S. West) Cavacini is proposed. This highly tolerant to salinity taxon is currently only known from a few zones of Continental Antarctica. The absence of records of this taxon in Maritime- and Sub-Antarctica, Australia and South America seem to justify the classification of this species as “endemic to Continental Antarctica”.